Lose video to monitor + crashes/reboots while playing games

Hi there, I'm not sure what this means when this happens but I've been investigating and doing what I can on my side to try and fix this.

My Story: I started college with a dell XPS laptop and that thing was just hell, 7 times parts had to be replaced and repaired. So, I tried to get a desktop, like I had when I was kid. This is a used computer from a person I know is honest. It is just unfortunate that problems have occured a week after I've gotten it.

The problem: I was excited about getting this computer and I decided to run some high end games on it at its max to see what it could do. They all ran like a champ. FPS in 100s, not a bit of slow down or overheating. This worked okay for a few days.

Two days ago, I noticed that the computer would not boot with video going to the monitor. The light would stay orange when it was on. I fiddled with the video card inside, took it out and resetted it and it worked fine. However, I started getting the problem when running any kind of game, where the video would freeze for 5 seconds, and then reboot.

What I've tried: I've monitored the temperatures and they are fine, I don't know how to go into a diagnostic tool that will test to see if everything works. Dell had a thing where you'd press F12 at start up and it'd take you to something, but this is a gateway.
I've done a system restore and an update of drivers for the video card and motherboard and now it will only freeze and sometimes lose video.

Here is a list of the computer make up.
And a sample of errors from looking at manage of computer

I'll provide anything else you think that is needed.
My motherboard is a nforce 270i

Attached Files:

As far as your problems with crashing while playing high end games, it could be overheating because your fan sinc can't keep the CPU cool, download and run "speedfan" and while you're running the games minimise and check the tempuratures. With the screen not working, try another monitor to see if its your graphics and if it works then its your monitor that is dieing